The traditional strapdown inertial navigation system usually uses the gyroscope survey carrier's angular speed and the accelerator surveyed the ratio strength signal which carries on the inertial navigation. The gyroscope free strapdown inertial navigation system replaces the gyroscope with the accelerator which signal outputs compared to resolve carrier angular speed. As a result, inertia component only has accelerator which has the very high request to accelerator's precision and the aspect of elimination noise. Based on the fast Fourier transformation and the wavelet transformation, carries on de-noising processing to the accelerator belt chirp signal. The belt chirp signal was carried on with the conventional based on the Fourier transformation, carries on the analysis to the power spectrum, and to de-noise the signal. According to the wavelet transformation, the methods of wavelet threshold and multi-resolution analysis are used respective characteristic to de-noise the signal, and compares with the traditional de-noising method, obtains the result that the methods of wavelet transformation for de-noising has a better aspect on smoothness and similarity.